In an effort to clean up stale bugs, I'm marking this as Invalid for
Nova because the issue is in Cinder.
** Changed in: nova
Status: New => Invalid
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https://bugs.launchpad.net/bugs/2019190
Title:
[RBD] Retyping of in-use boot volumes renders instances unusable
(possible data corruption)
Status in Cinder:
New
Status in Cinder wallaby series:
New
Status in OpenStack Compute (nova):
Invalid
Bug description:
While trying out the volume retype feature in cinder, we noticed that after
an instance is
rebooted it will not come back online and be stuck in an error state or if it
comes back
online, its filesystem is corrupted.
## Observations
Say there are the two volume types `fast` (stored in ceph pool `volumes`) and
`slow`
(stored in ceph pool `volumes.hdd`). Before the retyping we can see that the
volume
for example is present in the `volumes.hdd` pool and has a watcher accessing
the
volume.
```sh
[ceph: root@mon0 /]# rbd ls volumes.hdd
volume-81cfbafc-4fbb-41b0-abcb-8ec7359d0bf9
[ceph: root@mon0 /]# rbd status
volumes.hdd/volume-81cfbafc-4fbb-41b0-abcb-8ec7359d0bf9
Watchers:
watcher=[2001:XX:XX:XX::10ad]:0/3914407456 client.365192
cookie=140370268803456
```
Starting the retyping process using the migration policy `on-demand` for that
volume either
via the horizon dashboard or the CLI causes the volume to be correctly
transferred to the
`volumes` pool within the ceph cluster. However, the watcher does not get
transferred, so
nobody is accessing the volume after it has been transferred.
```sh
[ceph: root@mon0 /]# rbd ls volumes
volume-81cfbafc-4fbb-41b0-abcb-8ec7359d0bf9
[ceph: root@mon0 /]# rbd status
volumes/volume-81cfbafc-4fbb-41b0-abcb-8ec7359d0bf9
Watchers: none
```
Taking a look at the libvirt XML of the instance in question, one can see
that the `rbd`
volume path does not change after the retyping is completed. Therefore, if
the instance is
restarted nova will not be able to find its volume preventing an instance
start.
#### Pre retype
```xml
[...]
<source protocol='rbd'
name='volumes.hdd/volume-81cfbafc-4fbb-41b0-abcb-8ec7359d0bf9' index='1'>
<host name='2001:XX:XX:XXX::a088' port='6789'/>
<host name='2001:XX:XX:XXX::3af1' port='6789'/>
<host name='2001:XX:XX:XXX::ce6f' port='6789'/>
</source>
[...]
```
#### Post retype (no change)
```xml
[...]
<source protocol='rbd'
name='volumes.hdd/volume-81cfbafc-4fbb-41b0-abcb-8ec7359d0bf9' index='1'>
<host name='2001:XX:XX:XXX::a088' port='6789'/>
<host name='2001:XX:XX:XXX::3af1' port='6789'/>
<host name='2001:XX:XX:XXX::ce6f' port='6789'/>
</source>
[...]
```
### Possible cause
While looking through the code that is responsible for the volume retype we
found a function
`swap_volume` volume which by our understanding should be responsible for
fixing the association
above. As we understand cinder should use an internal API path to let nova
perform this action.
This doesn't seem to happen.
(`_swap_volume`:
https://github.com/openstack/nova/blob/stable/wallaby/nova/compute/manager.py#L7218)
## Further observations
If one tries to regenerate the libvirt XML by e.g. live migrating the
instance and rebooting the
instance after, the filesystem gets corrupted.
## Environmental Information and possibly related reports
We are running the latest version of TripleO Wallaby using the hardened
(whole disk)
overcloud image for the nodes.
Cinder Volume Version: `openstack-
cinder-18.2.2-0.20230219112414.f9941d2.el8.noarch`
### Possibly related
- https://bugzilla.redhat.com/show_bug.cgi?id=1293440
(might want to paste the above to a markdown file for better readability)
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